Crushing devices, such as a shredder are used, for example, to crush municipal waste or car tyres. A crushing device generally has at least one generally slowly rotating rotor, in which there are shredder elements to create a crushing effect. To achieve a suitable rotation speed, the crushing device generally has a power transmission containing gears, to which a hydraulic motor is connected. Electric motors can also be used, though a hydraulic motor will withstand large loading variations better than an electric motor. In practice, the rotor may even stop completely, which would cause problems in an electric-motor drive. The material is usually fed to the shredder from above while the crushed material falls below the shredder by gravity.
U.S. Pat. No. 5,052,630 discloses a shredder, in which various blades are fitted next to each other on a shaft, to form the rotor. The shaft itself is supported at both ends on large bearings in the frame structure of the shredder. In addition, a hydraulic motor is connected as a continuation of the shaft through a rigid clutch. The frame structure forms a throat, in which the rotor formed from the blades is located. In addition, counter-blades are fitted to both sides of the throat. Thus the drum can be rotated in both directions while crushing the material between the blades and the counter-blades.
In the shredder described above, as in other known shredders, large and complex bearings must be used. In addition, the bearings must generally be dismantled to be able to service the rotor. The rotor support of this kind also limits the maximum length of the rotor. In practice, the rotor deflects and otherwise flexes radially, which strains the bearings and may cause structural damage. In addition, in the above US patent the hydraulic motor is connected directly to the shaft, so that angular changes in the shaft also place a strain on the hydraulic motor, which is rigidly supported in the frame structure.